The present relates to the production and use of fiber surface treating agents, and particularly such agents containing a pyromellitate nucleus esterified by diverse alcohols, including a fluorinated alcohol.
U.S. Pat. No. 4,209,610 (Mare et al., 1980) discloses fluorinated pyromellitates useful as surface modifiers for polyamides and polyesters. One preferred group of compounds in that patent are those of the formula: ##STR1## wherein either formula A is a fluorinated ester such as CF.sub.3 (CF.sub.2).sub.p R'O(O)C-- and wherein B is HOCH(CH.sub.2 Cl)CH.sub.2 O(O)C--. R' is ethylene and p is a mixture of integers such as 3, 5, 7, 9 and 11 for different chains. Such products are formed by the reaction of pyromellitic dianhydride (PMDA) with a fluorinated alcohol, and then the reaction of the product diacid/diester with epichlorohydrin. Specifically, the product is produced by reaction of two moles of fluorinated alcohol with each mole of PMDA to form the diacid/diester. Each mole of the diacid/diester is then reacted with two moles of epichlorohydrin to produce the product. Because the oxirane may react at the one or two carbon, the product will normally contain minor amounts of material with B being HOCH.sub.2 CH(CH.sub.2 Cl)O(O)C-- (the product with a pendant primary alcohol) as well as major amounts of material with B being HOCH(CH.sub.2 Cl)CH.sub.2 O(O)C-- (the product with a pendant secondary alcohol). Other patents relating to the production of this product include U.S. Pat. No. 4,252,982 (Oxenrider 1981) wherein an ester solvent is used and U.S. Pat. No. 4,321,403 (Oxenrider et al., 1981) wherein N-methyl pyrrolidone is used as solvent. Methods for applying the compound in aqueous emulsions to fibers are disclosed in U.S. Pat. Nos. 4,192,754 (Marshall et al., 1980), 4,134,839 (Marshall 1979), 4,190,545 (Marshall et al. 1980), 4,193,880 (1980), 4,283,292 (Marshall 1981 ) and 4,317,736 (Marshall 1982).
While the use of these fluorinated pyromellitates results in treated fibers with high resistance to soiling, which resistance persists after a substantial number of laundering cycles, a need exists for fiber surface modifiers whose soil resistance persists over still more laundering cycles (representing extended use in environment such as carpets). Furthermore, as described in each of the above patents, an annealing step is employed after the application of the compound to the fiber. It would be desirable to be able to lower the temperature of the annealing step, for energy savings and to improve throughput, without impairing either the initial soil resistance or the retention of soil resistance after laundering.